. >> so, you're happy with his demeanor and energy level tonight? >> what i'm happy with is the path he wants to lead this country on. >> reporter: even while cheering the president today, his supporters seemed puzzled by his debate performance. >> i didn't know quite what was going on as far as maybe he's dealin with some crisis in the middle east. >> reporter: and battleground states like colorado and ohio, undecided voters nbc gathered to watch the debate say they saw something new. >> governor romney just sort of stepped up his game in terms of bringing something new to this campaign. >> it did change the way i thought about him. i liked him better. >> reporter: it was the most heavily tweeted in history. even big bird was a hot topic. this went viral. if mitt romney wins, this is what i'll be forced to do. this tidal wave of real time commentary on social media is just another uncontrollable factor that campaigns struggle to deal with as they try to get their messages out. >> john yang sampling the reaction in chicago and elsewhere. peter alexa